The point of this is to say that they must have some form of control to prevent misuse of their free "global state" resources, as they are necessarily limited. Nostr doesn't have such issue because each server is the private property of someone and has their own arbitrary rules. Bluesky the platform must have some arbitrary rules too otherwise it would be spammed to death, but then it is not really an open network anymore and whoever decides what is spam and what isn't has all the censorship power any other closed platform has.